Somerset County Council

Habitat evaluation procedure


Biodiversity is continuing to decline and new ways of tackling this need to be implemented. The Somerset Habitat Evaluation Procedure (HEP) methodology is employed for calculating the value of the habitats on a site for important species, the result of which is used in determining the amount of habitat replacement that would be required to mitigate for that lost to land use change. 

The HEP was first used operationally within a Habitats Regulations Assessment (HRA) carried out to determine the effects of development north of Taunton on the lesser horseshoe bat colony at the Hestercombe House Special Area of Conservation from site allocations in the draft Taunton Deane Borough Council Core Strategy in 2008. The use of the HEP was agreed to by Natural England. Since that date the methodology has evolved and been used in over thirty cases, both for plans and projects, within HRA and in Ecological Impact Assessments, and at the various stages in the planning process from site allocation, pre application through to the planning application stage. 

The HEP is structured around the calculation of Habitat Units (HU), which are the product of a Habitat Suitability Index (scores for the quality of different habitats for a particular species) and the total area of habitat (quantity) affected by a development proposal. 

The objectives of the Habitat Evaluation Procedure include:

  • to form a sound basis for the allocation of sites in local authority Local plans/core strategies
  • provide an upfront estimation of likely ecological mitigation requirements to developers, removing some of the uncertainty inherent in taking forward strategic sites through the planning process 
  • deliver smoother progress through the planning application and determination process by removing conflicts with biodiversity and reducing the likelihood of delays
  • fulfil local authority statutory obligations for the conservation of biodiversity
  • enable a quantitative rather than subjective approach to biodiversity impact mitigation 

Our Habitat Evaluation Procedure methodology has been successfully employed for developments north of Taunton, for the Hinkley new build site clearance works and other sites across the County. The HEP is now being included in technical guidance commissioned by Natural England on the Special Areas of Conservation (SAC) designated for bats in the County and North Somerset (currently in development).

The Habitat Evaluation Procedure methodology to be used in Somerset is available under the Information and Resources section to the right.

Who can use it?

The Habitat Evaluation Procedure can be applied to inform:

  • Site allocations in the following plans: The Local Plans for Mendip, Sedgemoor, South Somerset District, West Somerset and Taunton Deane Borough Councils and Somerset County Council plans; 
  • Master planning of proposed development sites pre application; and
  • Planning applications, including as a check for the adequacy of mitigation provided by an application within Habitats Regulations Assessments and Ecological Impact Assessments.

What is covered?
The following development projects will have their ecological mitigation and/or compensation requirements calculated using Somerset's Habitat Evaluation Procedure methodology across the county: 

  • strategic sites
  • infrastructure schemes
  • large-scale developments
  • all developments with the potential to cause significant impacts to protected and/or priority sites, species and habitats  

The Natural Choice: Securing the Value of Nature. - the Government White Paper on the Natural Environment
The White Paper highlights the potential for biodiversity offsetting, which focuses on the impact of development. The proposals intend to improve the delivery of planning policy requirements relating to biodiversity in a cost-effective and measurable way, by providing a straightforward approach to assessing the impact of the development, agreeing the compensation requirements and demonstrating compliance. The HEP can be seen as a form of biodiversity offsetting.

National Planning Policy Framework
The planning system should contribute and enhance the natural environment by minimising impacts on biodiversity and providing net gains in biodiversity, including establishing coherent ecological networks that are more resilient to current and future pressures. When determining planning applications, if significant harm resulting from a development cannot be avoided, adequately mitigated or, as a last resort, compensated for, then planning permission should be refused. The HEP aims to quantity impacts on species populations so that no net loss or net gain can be demonstrated.

Biodiversity 2020: A strategy for England's Wildlife and Ecosystems Services 
Details a strategy for delivering the Government's natural environment policy. It includes a commitment to '...take a strategic approach to planning for nature'. The HEP can be used to predict land use by a species, using GIS mapping, at a strategic level.

Laws and regulation

European Directive 92/43/EEC on the conservation of natural habitats and wild fauna and flora
Council Directive 2009/147/EC on the conservation of wild birds
Conservation of Habitats and Species Regulations 2010
The Conservation of Habitats and Species (Amendment) Regulations 2011
Natural Environment and Rural Communities Act 2006


Contact: Ecologist, Somerset Ecology Services 
Address: Planning Control, Somerset County Council, County Hall, Taunton, TA1 4DY
Phone: 01823 358118 
Fax: 01823 356114
Opening Hours: Monday to Friday 8am to 6pm, Saturday and Sunday closed.

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